This invention relates to adjustable seat structure, and more particularly to bilateral, warp-tolerant, cross-synchronized, gear-lock mechanism for selectively adjusting, and for releasably gear-locking, the inclination of a seat-back sub-structure (seat-back) in relation to a seat-base frame (seat-base) to which the seat-back is pivoted. While the invention has utility in many applications, it is described and illustrated herein in the setting of an aircraft passenger seat—a setting with respect to which its utility has been found to be especially well suited.
The terms “bilateral” and “cross-synchronized” refer to the facts (a) that substantially duplicate gear mechanisms are employed, one each on opposite lateral sides of a seat, and disposed at the general location of the pivot axis which is provided for angular adjustment (inclination) of such a seat-back sub-structure, and (b) that a shared, rotation-transmitting lateral shaft connects two cams in these two mechanisms for coordinated operation and interaction, as will be explained. The term “warp-tolerant” refers to the important fact that the mechanism of this invention easily accommodates, with a generous “margin of safety” still remaining, the well-known, relatively severe “rack and roll”, orthogonal-axis, safety-qualifying twist test which certain passenger seats, such as those installed in aircraft, are required to pass.
As will be seen, the two, lateral-sides mechanisms of this invention each includes a unique, combined lever, gear and cam arrangement which operates smoothly, and bi-directionally positively, to free and anchor a seat-back selectively at a plurality of different inclinations relative to the associated seat-base. Much of the description given herein for the present invention is presented, for simplicity sake, in the context of just a single one of these mechanisms. Both mechanisms, however, are discussed at appropriate places where necessary to understand the cooperative interactions which take place between them.
According to the preferred and best mode embodiment of the invention which is specifically illustrated and described herein, three spaced, substantially parallel hinge, or pivot, axes play cooperative roles in the structure and operation of the laterally spaced mechanisms of the invention. One of these axes (the seat-back rock axis) is that with respect to which the seat-back swings, inclines, rocks, etc., reciprocally relative to the seat-base. In each lateral mechanism, a special rocker gear, which possesses an arc of gear teeth, is pivoted on this same axis. The rocker gear is anchored to the seat-back for movement as a unit therewith, and its arc of gear teeth follows a circular, chordal path (approximately 30°) which is radially centered on the seat-back rock axis.
A second axis is one on which a rockable latch element in each lateral mechanism, which element also possesses an arc of gear teeth, is pivoted for reciprocal rocking relative to the seat-base. The teeth in this latch element confrontingly face the teeth in the rocker gear, are distributed along a chordal, circular arc (about 20°) which has a radius of curvature substantially the same as that of the arc of teeth in the rocker gear, and, because both sets of teeth have the same (common) tooth-pitch, are freely meshable and de-meshable with the rocker gear teeth. The arc of teeth in the latch element is not fixedly centered on any of the mentioned, three pivot axes. Rather, the teeth in this second-mentioned arc swing, with rocking of the latch element, about the mentioned “second” axis. The latch element in each lateral mechanism, within its perimeter, is formed with a specially shaped void space which functions, as will be explained, to furnish special cam-follower dwell and drive surfaces (structures) that play roles in the operation of the invention.
The third axis defines a rock/pivot axis for a cam, or cam structure, in each lateral mechanism, which cam structure is specially shaped, and disposed operatively within the latch element's void space for interaction therein with the mentioned cam-follower dwell and drive surfaces. This cam structure is anchored to a rock-axis-sharing elongate shaft which carries, near one (or both of its) end(s), a user (seated person) manipulable lever which is employable to operate the mechanism of the invention. This shaft extends between the opposite lateral sides of a seat structure, and acts as a torque and rotation transmitting agency between the two cams in the two lateral mechanisms. Because of this structural arrangement, both cams function as a unit with one another.
Various other features and advantages of the invention will become more fully apparent as the description which now follows is read in conjunction with the several drawing figures.